Previous Biological Response Modifiers Program (BRMP) studies have shown that endogenous circulating NK and LAK cell activity can be induced and maintained for a prolonged period, using IL-2 twice weekly. In this regimen, IL-2 is given by 24-hour continuous infusion twice weekly for 3 weeks, at a dose of 30 mu/m2 (BRMP units) per 24-hour infusion. Subsequent IL-2 doses are adjusted in the individual patient to sustain high levels of CD56 positive cells in peripheral blood while allowing most treatments to be undertaken in the outpatient setting. Modest evidence of antitumor activity has been seen using this regimen in melanoma. Other studies of a monoclonal antibody, R24, to the UD3 antigen present on melanoma cells, have shown that this antibody given alone results in some antitumor activity in a minority of melanoma patients. Laboratory studies indicate that this antibody can mediate antibody-dependent cellular cytotoxicity (ADCC) using circulating large granular lymphocytes (LGL) cells produced by IL-2. This study was designed to investigate the combination of R24 in a series of escalating dose ranges, together with the IL-2 regimen previously investigated by the BRMP.